Three-wire screw thread gauge



Dec. 23, 1952 s. w. ROSS 2,622,337

THREE-WIRE. SCREW THREAD, GAUGE Filed Oct. 14, 1949 INVENTOR SYL V/A/V W 2085,

ATTORNEYS Patented Dec. '23, 1952 UNITED STATES OFFICE My invention relates to improvements in screw thread gages.

A primary object of my invention is to provide a screw thread gage which may be formed from a single continuous section of accurately calibrated hardened steel wire, or the like.

A further object is to provide a highly simplified thread gage for use in forming screw threads upon a lathe, or the like, and adapted to accurately gage a wide range of thread diameters for a given number of threads per inch.

A further object is to provide a thread gage which is extremely simple to use and which requires no data other than the outside diameter of the thread being formed.

A further object is to provide a wire screw thread gage, wherein the maximum outside diameter of the screw threads being formed, plus a simple constant will equal a measurement over the wires of the gage.

A still further object is to provide a wire screw thread gage for use by machinists and inspectors, which will be comparatively cheap to manufacture, long lasting, accurate, and requiring no special mathematical knowledge or dexterity.

Other objects and advantages to my invention will be apparent during the course of the following description.

In the accompanying drawings:

Figure 1 is a plan view of a screw thread gage embodying my invention.

Figure 2 is a side elevation of the same.

Figure 3 is a side elevation of the gage, drawn on a reduced scale, and illustrating the use of the same, and

Figure 4. is a greatly enlarged transverse vertical section taken on line 4-4 of Figure 3.

In the drawings, the numeral l designates generally my screw thread gage which may be formed from a single continuous strand or section of accurately calibrated and hardened steel wire, or the like. The wire of the gage should be relatively stifi and yet resilient enough to engage over shafts of different diameters. The gage ll) comprises laterally spaced opposed elongated parallel sides I I and I2 and the entire gage I0 is relatively narrow and elongated in the longitudinal direction of the sides II and I2. The side l2 comprises a single straight strand or rod [3 of the wire of the gage, bent at its opposite ends to form helical coils l4 and [5 of approximately one and a half turns each. The coils l4 and I5 are integral with the side I3 of the gage and form parts of the single continuous strand of wire. The wire is further bent atthe ends of the coils l4 and I5 remote from the side 13 to form a pair of straight elongated longitudinal strands or rods I6 and I1, arranged in laterally opposed substantially contacting relation, as shown in Figure 1, when the gage is not in use for measuring the diameter of screw threads. The strands l6 and I1 constitute the side ll of the gage and they are spaced equidistantly of the strand l3, Figure 2, and when in use for gaging a thread, Figure 4, the strands l5 and [1 are adapted to spread apart laterally equidistantly upon both sides of the strand E3. The free ends I8 and :9 of the strands l6 and l! terminate near and inwardly of the coils l5 and M, respectively, as shown. Small sleeves 2B engage slidably about the strands I6 and H for securing them together, and these sleeves are slidable longitudinally of the strands l6 and H, but are normally arranged near the ends [8 and I9, so that the strands l6 and I1 may be spread apart slightly between the sleeves 20.

An attaching ring 2| is secured within the coil l5 as shown, and a flat metal tag 22 is secured to the ring 2|, and is provided upon one side with indicia 23, stamped or otherwise permanently marked thereon. The indicia 23 preferably takes the form of a first line 24 which reads Max. 0. D. This is the maximum outside diameter of the thread to be gaged while being turned on a lathe, or the like. There is a second line 25 which takes the form of a simple numerical constant to be added to the maximum outside diameter of the screw thread to equal the diameter or measurement over the sides H and I2 of the gage, constituting a third line 26 which reads M. 0. W. The gage can be opened up or taken apart by pulling the strands l6 and I! out of the sleeves 20. With the strands thus disengaged from the sleeves, the gage may be passed over a shaft, screw, or the like, and the strands may then be reinserted in the sleeves 20.

In use, the gage may be employed to accurately measure threads being formed upon a lathe. The tail stock of the lathe may be backed up so that the gage l0 may be passed over the shaft S having threads t turned thereon. The sides H and #2 may be spread apart to assume somewhat bowed shapes as shown in Figure 3. The strands It and I? are spread apart slightly, Figure 4, for engaging between alternate threads t upon one side of the shaft S. The strand l3 engages between two adjacent threads 1? at a point diametrically opposite and midway between the strands i5 and H. The strands l3, l6, and Il Will project radially beyond the outside diameter of the threads, and the anvil 21 and screw 28 of a standard micrometer caliper 29 may be passed over strands l3, l8 and [1, Figure 4, for measuring the diameter or measurement over the strands of the gage. By adding the constant 25 to the maximum diameter of the screw thread being formed, the measurement over the strands of the gage may be obtained. This measurement over the strands may be checked at intervals, during the formation of the threads, until the threads are cut to their proper diameter. It is not necessary for the machinist to know the pitch diameter of the threads, or any other technical information.

One of the gages IE! will sufiice for measuring a large range of thread diameters, for a given pitch, or threads per inch screw. Beyond the wide range of diameters, additional gages may be provided and formed of different size wire, to measure different pitch screw threads. In any event, a minimum number of gages H3 will suffice for measuring all popular'standard sizes of screw threads. One of the gages It! is adapted for use on screw threads of two different pitches,-or numbers of threads per inch, such as 32 or 36 threads per inch. For exampleone gage I may be used for measuring 32 and 36 threads per inch screws, up to diameter of I an inch and a quarter. The indicia on the tag 22 for measuring '32 pitch threads, and 36 pitch threads will obviously be different, since theconstant to be added to the outside diameter of the screw threads is difierent for each pitch. Accordingly, the indicia for the 32 pitch screw threads will be indicated upon one side of the tag 22, and the indicia for the 36 pitch threads will appear upon the opposite side of the tag.

Since the gage is elongated, and the sides ii and 12 are long and resilient, the gage is particularly useful in lathe work, because when the tail stockis backed away the gage may be slipped over shaft diameters which are larger than the threads to be gaged.

It is to be understood that the form of my invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in shape, size, and arrangement of parts may be resorted to, without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. In a screw thread gauge, a pair of elongated normally straight resilient sides, said sides being co-extensive and laterally spaced from each other, to engage between threads at opposite sides of a screw, means fixedly connecting together the adjacent ends of the sides, one of said sides consisting of two separate overlapping strands extending longitudinally inwardly from said means and having inner ends terminating in longitudinally spaced relation to the ends of the sides, said separate strands being normally in laterally contacting relation, and longitudinally slidable means embracing said separate strands and arrangedto occupy positions along said separate strands wherein said separate strands are maintained in lateral contact and positions in which said separate strands can be spread apart.

2. In a screw-thread gauge, a pair of elongated coextensive sides, means extending between and connected to adjacent ends of said sides and normally holding said sides in parallel, spaced relation, one or" said sides consisting of a single straight rod arranged to engage the groove between adjacent screw-threads at one side of a threaded member, the other side of the gauge consisting of a pair of straight rods arranged in side-by-side relation, said rods of'the pair being arranged to engage in the grooves at the opposite sides of a thread at the opposite side of the threaded member from said single rod, said rods of the pair extending longitudinally inwardly from different ones of said means and having longitudinally inward free ends terminating in longitudinally spaced relation to said means, said means being resilient and normally serving to maintain said other side of the gauge parallel to said one side thereof, and slidable'means embracing said pair of rods to maintain saidpair of rods in lateral contact with each other.

3. In a screw-thread gauge, a pair of elongated coextensive sides, means extending between and connected to adjacent ends of said sides and normally holding said sides in parallel, spaced relation, one of said sides consisting of .a single straight rod arranged to engage the groove between adjacent screw-threads atone side of a threaded member, the other side, of ,thegauge consisting of a pair of straight rods arranged in side-by-side relation, said rods ,of the pair being arranged to engage in the grooves atv theopposite sides of a thread at the oppositeside of the threaded member from said single rod, said rods of the pair extending longitudinally inwardly from diiferentones of saidmeans. and having longitudinally inward free ends terminating in longitudinally spaced relation to said means, said means being resilient and normally serving to maintain said other side ,of the gauge parallel to said one side thereof, said pair of rods having longitudinally ,slidable sleeves thereon, said sleeves being slidable on the rods to engage the free ends of the rods to hold the rods against being laterally separated from each other.

SYLVIAN W. ROSS.

REFERENCES CITED The following references are of reccrd-in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,875,726 Hartness Sept. 6, 1932 2,399,624 Bunch May '7, 1946 2,443,820 Gabbey June 22, 1948 FOREIGN PATENTS Number Country Date 49,164 Sweden May 11, 1921 107,855 Great Britain July 19, 1917 583,385 GreatBritain Dec. 17, 1946 OTHER REFERENCES Publ.: Popular Science, April 1944, page 172. 

